On site application of paint directly to a surface to be decorated is the time-honored method for providing a graphic design, such as a decorative design. While such a process provides many aesthetic and physical features, including realistic appearance, color flexibility, durability to abrasion, weathering and chemical attack, it also suffers from many disadvantages. For example, relatively skilled labor is necessary. Long application times are usually the rule, and potential contamination to adjacent areas, particularly mechanical equipment, can occur. Accordingly, prefabricated film graphics have been utilized to avoid many of these disadvantages. Such film graphics, often called "decal" or "transfer graphic", when utilized on the exterior surface of vehicles, typically require extreme resistance to abrasion and chemical attack because of exposure of the vehicle surfaces to various atmospheres or environments. Accordingly, such graphics must generally be provided with a protective clear coat over the graphic areas.
This protective clear coat can be located in registry with the graphic area by applying a continuous layer of clear coat over the graphic and non-graphic areas, and subsequently cutting through the several layers precisely at the outline of the graphic area, typically called "die cutting" or "kiss cutting". This approach results in substantially vertical or right angle edges of the graphic and protective clear coat which can collect dirt, wax, and other foreign materials which can detract from the aesthetics of the applied graphic design. Responsive thereto, a sealing agent, e.g., SCOTCHCAL Brand 4150 Edge Sealer, available from the Minnesota Mining and Manufacturing Company ("3M") may be applied about the edges of such a graphic after application to the vehicle. The sealing agent protects the exposed sides of the graphic and adhesive from chemical attack and reduces the mechanical forces acting thereon. This technique is most typically practiced in the airline industry.
A second approach is to apply the protective clear coat only to graphic areas, as, for example, by screen printing, or utilizing a stencil with an open area corresponding precisely to the outline of the graphic design. Those skilled in the art are aware of the difficulty encountered with such a process, because of factors such as dimensional changes in the film substrate, tension variables in the screen mesh, and accurate positioning of the substrate in registry with the stencil. Small graphics, such as those with overall dimensions of not greater than about 12 inches.times.12 inches (30 centimeters.times.30 centimeters) can generally be manufactured with satisfactory registration by those having requisite skill. However, this becomes much more difficult for larger graphic areas, and particularly for decorative items such as pin stripes which are common for the vehicle or automotive market.
U.S. Pat. No. 4,356,617 (Coscia) discloses the formation of a raised dike around a graphic design for the purpose of controlling the flow of a coating composition applied thereto. The reference further teaches that such flow may also be controlled by a groove or gap around the design if the coating composition has sufficient surface tension. U.S. Pat. Nos. 4,332,074 (Auld et al.) and 4,605,575 (Auld et al.) disclose utilization of integral bezels for similar purpose. Such techniques do not provide application of the protective clear coat to the adhesive layer which adheres the graphic design to a desired substrate, thereby leaving the edges of the adhesive exposed and subject to collection of foreign materials and environmental degradation.
Yet another approach which could be utilized is to apply the protective clear coat with a substantial oversize border to assure complete coverage of the graphic area. While this method achieves the required objective of protection for the graphic design, it is generally considered not to be aesthetic.
Application Ser. No. 846,754, filed Apr. 1, 1986, commonly assigned herewith, discloses a graphic pattern having a protective coating thereon in exact registration therewith and a process for forming the same. It is taught that adhesive may be applied to the bottom of the coated graphic for application to a substrate. According to the process disclosed therein, an imaging composition, which has sufficient surface tension to wet a carrier, is applied, e.g., by screen-printing, to the carrier and dried to form a graphic pattern thereon. A liquid protective coating is applied over the graphic pattern in an oversize border therewith. The protective coating has sufficient surface tension to wet the graphic pattern but not the carrier surface whereby during drying the protective coating will dewet the major surface of the carrier to provide exact registration with the graphic pattern. Following drying of the protective coating, the article is laminated to a premask tape, the carrier is removed and an adhesive is applied to the underside of the graphic pattern for subsequent transfer to a substrate. Although detailed transfer graphics may be achieved by such method, the adhesive is not covered by the protective coating, thus resulting in exposed edges subject to collection of foreign materials and environmental attack.
Although application of a protective clear coat by screen printing is a typical technique, other methods such as roller coating or spray coating may also be considered, providing a dry film thickness of from about 0.5 to about 4 mils (0.01 to 0.1 millimeters) thickness is achieved.
Summarizing, an acceptable protective clear coat should be of sufficient thickness to provide adequate wearability and resistance to chemical environments, and precisely cover the graphic area, whether same be large or small, and whether it be a simple geometric shape, such as a narrow width line, or a complex intricate design. An acceptable protective clear coat should further cover the adhesive means which secures the graphic to the substrate thereby inhibiting unsightly collection of foreign matter and protecting the adhesive. Known techniques described above do not satisfy all these requirements.
Accordingly, the present invention provides precise registration of a clear protective coat over a graphic pattern and underlying adhesive; the protective coat has tapered, rounded and sloping edges which seal the edges of the graphic pattern and adhesive, thereby inhibiting the buildup of wax and foreign matter at the edge portions, and looks integrated with the substrate; i.e., provides a paint-like look; the process can accommodate varying process tolerances, operator variability and equipment tolerances; and the process provides a lenticular appearance on thin pin stripes, such as may be placed on vehicle surfaces.